1. Field of Invention
The present invention relates to semiconductor devices and methods of fabricating the same. More particularly, the invention relates to a semiconductor device in which an overcoat film is formed o n the edge and side faces of each IC chip obtained by dicing a semiconductor wafer, and a method of fabricating the same.
2. Description of Related Art
FIGS. 7(a) to 7(c) are sectional views showing steps in a related art method of fabricating a semiconductor device.
In the fabrication process of the semiconductor device, as show in FIG. 7(a), a chip electrode 103 is formed on an IC pad section (not shown in FIG. 7(a)) in a semiconductor wafer 101 on which elements are formed.
Next, as shown in FIG. 7(b), in order to protect the active surfaces of the IC chips, an overcoat film 105 composed of a photosolder resist or the like is formed over the entire upper face of the semiconductor wafer 101 including the chip electrode (or bump) 103. Such as a polyimide or silicone resin may also be used for the overcoat film 105.
A photoresist film (not shown in FIG. 7(b)) is then formed on the overcoat film 105, and a resist pattern having an opening above the chip electrode 103 is formed on the overcoat film by exposing and developing the photoresist film. The overcoat film 105 on the chip electrode 103 can then be etched using the resist pattern as a mask. Alternatively, photoetching can be performed using a light-shielding mask. Thereby, as shown in FIG. 7(c), the chip electrode 103 is exposed. If necessary, a thick electrode can then be formed.
Next, dicing is performed in order to divide the semiconductor wafer 101 into individual IC chips. In the dicing step, the semiconductor wafer is cut with a dicing saw (not shown in FIG. 7(c)).
Scribed lines (not shown in FIG. 7(c)) are formed on the upper face of the semiconductor wafer 101. Preferably, the width of the scribed line is larger than the width of the dicing saw by approximately 20% to 30%. For example, when the dicing saw has a width of approximately 100 μm, the width of the scribed line is set at approximately 120 μm.
Next, first dicing (half cutting) is performed along the scribed lines. In the first dicing step, about a half of the thickness of the semiconductor wafer is cut. Dicing traces are thereby formed on the upper face of the semiconductor wafer 101.
Next, second dicing (full cutting) is performed along the dicing traces from the upper face side of the semiconductor wafer. In the second dicing step, the remaining thickness of the semiconductor wafer that is not cut in the first dicing step is cut. (For example, approximately 20% of the thickness of the semiconductor wafer is cut.) The semiconductor wafer 101 is thereby divided into individual IC chips. The second dicing is performed at a processing rate of approximately 70 mm/sec in order to prevent the IC chips from being damaged or to reduce such damage. In such a case, the revolving speed of the dicing saw is approximately 40,000 rpm.
Instead of the second dicing (full cutting), cracking may be performed to divide the semiconductor wafer 101 into individual IC chips.
FIGS. 8(a) to 8(c) are sectional views showing steps in another related art method of fabricating a semiconductor device. The same reference numerals are used for the same components as those in FIGS. 7(a) to 7(c), and only the different parts are described.
First, as shown in FIG. 8(a), a semiconductor wafer 101 is prepared on which elements are formed, and an overcoat film 105 is formed on the entire upper face of the semiconductor wafer 101.
Next, as shown in FIG. 8(b), an opening is formed in the overcoat film 105 at the position above an IC pad section (not shown in FIG. 8(b)). A chip electrode 103 is then formed in the opening.
As shown in FIG. 8(c), dicing is performed in order to divide the semiconductor wafer 101 into individual IC chips.